Targeting economic and environmental benefits associated with the integration of regeneration units in water systems

Water treatment is traditionally seen as an "end-of-pipe" solution to deal with contaminated water satisfying discharge regulations at a minimum expense. However, the reuse of treated water as regenerated water is a promising strategy to counteract water scarcity. This approach to transform waste into resources is motivated by the circular economy paradigm. This study presents a mathematical programming approach to target both the environmental and economic benefits of water systems by introducing additional regeneration units to close the loop. In addition to water users and authorities, the approach also considers operators and dealers, which are revealed as key stakeholders. Hence, the feasible region of the regeneration units design specifications is determined and visualized through a multi-objective optimization approach targeting the systems operating cost and freshwater consumption. Its application is demonstrated on a benchmark case study from the literature, revealing a potential economic benefit of 37.5% and a freshwater reduction of 80.9% over the case without regeneration units. Furthermore, we show that a cooperative exchange strategy leads to higher benefits compared to the solutions presented in the literature. Finally, we demonstrate how the barrier plots introduced in this work can be used by different stakeholders in the water market to support their decision-making.Peer ReviewedPostprint (published version

Information retrieval from scientific abstract and citation databases: A query-by-documents approach based on Monte-Carlo sampling

The rapidly increasing amount of information and entries in abstract and citation databases steadily complicates the information retrieval task. In this study, a novel query-by-document approach using Monte-Carlo sampling of relevant keywords is presented. From a set of input documents (seed) keywords are extracted using TF-IDF and subsequently sampled to repeatedly construct queries to the database. The occurrence of returned documents is counted and serves as a proxy relevance metric. Two case studies based on the Scopus® database are used to demonstrate the method and its key advantages. No expert knowledge and human intervention is needed to construct the final search strings which reduces the human bias. The methods practicality is supported by the high re-retrieval of seed documents of 7/8 and 26/31 in high ranks in the two presented case studies.Peer ReviewedPostprint (author's final draft

Towards automated information retrieval of process data and knowledge from academic databases

Process modeling requires both data (chemical reaction yields, kinetic constants, cost estimates, environmental indicators, etc.) and knowledge (operation models and formulations, alternative processes and technologies, etc.). Searching in databases and published research may provide such information, but there is a lack of systematic methods and tools guiding this procedure. The present work describes and assesses an information retrieval methodology that is part of a proposed retrieval and extraction cycle addressing this problem. Two query construction methods for sampling academic databases are proposed, assessed and compared. Departing from a seed corpus of a limited number of papers, Scopus® is used as an academic database to retrieve literature containing information associated with pyrolysis processes of waste plastic. It is found that, with minimal human intervention, the methodology is able to return a ranked list of candidate documents that have a considerable (linguistic) relevance.Postprint (published version

Profit allocation in industrial symbiosis networks: utility exchanges

Industrial symbiosis networks enable efficient resource sharing between companies and, thereby, generate otherwise unachievable profits. This work studies the multi-actor process integration problem that arises when addressing utility exchange involving different companies. The aim is to find stable profit allocations by combining process integration principles with game theory methods. The profit table provides the necessary information to solve the cooperative game that takes place in the industrial park. For the case study, a simplified utility exchange model is developed and the proposed decisionmaking framework is applied to it, in order to highlight the importance of knowledge about the potential pitfalls of the employed profit allocation methods.Postprint (published version

A MILP model for enhancing wastewater networks by introducing reclaimed wastewater usage

Wastewater treatment plants (WWTPs) are an example of available but underutilized waste-to-resource processes. Economic benefit opportunities can be generated through the design and operation of WWTPs following a circular economy policy. At the same time, the environmental performance is also enhanced, since water scarcity is counteracted by replacing freshwater usage with reclaimed water. In this work, we develop a MILP mathematical model representing the main characteristics of multi-contaminant wastewater exchange networks and validate it through a case study that is inspired of a WWTP located in Barcelona, Spain. As a result, we find an optimal network that can reduce the water treatment cost from 0.404 €/m³ to 0.312 €/m³. Moreover, the model allows considering the possibility of retrofitting the existing WWTP by constructing an additional treatment line and drawing the barriers for this line to achieve the targeted wastewater treatment cost. These results demonstrate that changing the role of WWTPs from an “end-of-the-pipe” solution towards a waste-to-resource route bears an unexplored potential that should be considered by all actors in the water market.Postprint (published version

Economic and environmental assessment of plastic waste pyrolysis products and biofuels as substitutes for fossil-based fuels

The global economy is shifting toward more sustainable sources of energy. The transportation sector is a remarkable example of this fact, where biofuels have emerged as promising alternatives to traditional fossil fuels. This work presents a techno-economic and environmental assessment of existing liquid fuels in hard-to-decarbonize sectors and their emerging renewable substitutes. The comparison focuses on fossil-based, biomass-derived, and plastic waste-sourced fuel alternatives that can be used in spark-ignition (gasoline) and compression-ignition (diesel) engines. Results for diesel substitutes prove the superior performance of plastic waste pyrolysis oil in terms of production cost reduction (-25% compared to diesel) and “well-to-tank” life cycle impact reduction (-54% human health, -40% ecosystems, -98% resources). Consequently, research and development toward the conversion of plastic waste into fuels should be extended to make the technology more accessible and robust in terms of fuel quality. On the contrary, the results for gasoline alternatives are not as conclusive: bioethanol and ethanol from plastic pyrolysis have a considerably lower impact on resource scarcity than gasoline (-80% and -35% respectively) and higher on the other two life cycle endpoint categories, but they have higher production costs compared to gasoline (+57% and +130% respectively). While blends of gasoline with pyrolysis-sourced ethanol can reduce the impact on human health and ecosystems, blends with bioethanol have a lower impact on resource scarcity and increase economic profitability. This allows fuel providers to offer tradeoff solutions in the form of blends based on their priorities.Peer ReviewedPostprint (published version